There are many common trends among Japanese women that I have had the opportunity to observe firsthand. Before coming to Japan, I laughed off most of these as rampant stereotypes or myth, but much to my surprise (and horror, in some cases), they are generally quite true.
Japanese women are pigeon toed : which is called "uchimata" in Japanese, and definitely not considered to be a posture problem. From childhood, women are encouraged to walk in this manner, which has been considered elegant and womanly since at least as far back as the Edo period. If you ever go to a Kabuki play, you will notice that all the onnagata (male actors playing female parts) will walk in this fashion, as it is supposed to insinuate a womanly gait.
The pigeon-toed-ness is never more apparent than when one takes a walk through the streets of Tokyo after dark. Almost all women wear ridiculously high heels (usually in the form of knee-high boots paired with tiny skirts), a phenomenon that does not mix well with their way of walking. It's quite painful to witness, in all honesty : women walk with these insanely high heels, a difficult feat in itself, but when paired with being pigeon-toed, the heels are forced to unnatural angles and actually bend 90 degrees, causing the woman to walk sideways on the heels, which, instead of remaining vertical, are now parallel to the ground. It looks terribly painful.
Japanese women are incredibly indulgent mothers : there is an absolute lack of any discipline whatsoever in Japan, at least when it comes to the mother's role. The mother-child relationship is referred to as "amae," meaning something like "indulgent dependency." While it is most apparent in the mother-son relationship, I've seen the same attitude displayed from mothers to their female offspring as well.
Perhaps one of the main reasons for spoiling children in Japan stems from the fact that most couples only have one or two children (yes, the population is in decline). While in many other countries parents don't hesitate to tell their children what to do, even if it involves reprimanding the object of their affection, in Japan children are given free reign by their mothers to wreck havoc in every direction, even in public. When a child misbehaves, the mother is more likely to say something along the lines of, "wouldn't you rather have some candy than pull that woman's hair?" instead of telling the kid to shape up and sit still.
This attitude also likely stems from the Confucian principle that women must serve their father, then their husband, and then their son.
Japanese women quit their jobs upon getting married : while this is becoming less prevalent as the society adopts more "western" ways, it is still overwhelmingly common. Some women will begin to work again after their children are in school, but usually only part-time, and usually not at all.
The reasons behind this decision are simple : women are expected to keep the household running smoothly, a role that hasn't changed in hundreds of years. The husbands almost never lift a single finger to help around the house, which is perfectly accepted and, indeed, expected. A woman simply would not have time to maintain the house and look after the children while working full-time (theoretically).
Japanese women are bow-legged : well, so are Japanese men, really. It comes from practicing 正座 ("proper sitting") from a young age and there's really nothing to be done for it short of rearranging the culture. Shigata ga nai.
Japanese women do everything in their power to appear childlike : this is far and above the most disturbing characteristic I've been confronted with. Girls and women seem to be set against behaving in any sort of mature manner, instead preferring to speak in high, affected voices, employ almost laughable facial expressions (batting eyelashes, pouting incessantly), and wear schoolgirl skirts even after graduation.
The most obvious reason is because they're encouraged to do so. Men see such behavior as incredibly sexy (god knows why), and it is closely tied with the fetishism that Japan is notorious for. It's not uncommon to see a woman in her mid twenties on the train clutching a stuffed animal and wearing a frilly pink dress covered in lace and bows complete with pink Mary Janes, a combination that would make any "western" child of six wrinkle her nose in disgust.
Japanese women try to look "western" : attempting to appear "western" is relatively obvious in the culture as a whole, but it is at its strongest when it comes to women. While during the Meiji Era women were expected to uphold Japanese traditional values while the men adopted "western" ways, the Japanese attitude seems to have done a 180. Women are assaulted with all sorts of products telling them they must change their appearance to look more caucasian. For example, if you ever stroll through the cosmetics section of a pharmacy, you will see a never-ending display of eyelash curlers, fake eyelashes, whitening lotions, eyelid putty (all the convenience of having a fold in your upper eyelid without resorting to blepharoplasty like a certain J-pop artist), etc. etc..
This is also apparent in common fashions. For example, many schoolgirls wear massive white socks that resemble legwarmers (and yes, people still wear true legwarmers as well), which are often called "slouch socks" or "loose socks" or something along those lines. The reason behind these socks is said to be that Japanese girls are trying to make their legs look longer and more "American."
I hope this information will be of some use, whether in breaking or confirming stereotypes or lessening the